The present invention relates generally to safety lights, such as barricade lamps that are commonly found at road construction sites. Safety lights, which are typically mounted on barricades, are designed to warn others of construction workers and other safety hazards. Such safety lights are deployed in areas remote from established power supplies, and typically depend on batteries to supply power to the light. Generally speaking, there are two different types of batteries, rechargeable and non-rechargeable. Each of these battery types has advantages and downsides.
Non-rechargeable batteries are commonplace, relatively inexpensive, and are capable to providing necessary power to a safety light. A downside for such batteries, however is that they are somewhat variable in their lifespan. This is due to numerous factors including variability in manufacturing, different producers, and unknown loss of power stored in the batteries during the period between manufacture and use. Environmental factors, such as temperature, also affect the lifespan of such batteries. As such, it is very difficult to predict with any certainty when non-rechargeable batteries for a safety light are running low or about to stop working altogether. If the batteries in a safety light run down, the ability of the safety light to warn of hazardous situations is greatly diminished. Moreover, due to the large number of safety lights typically found at a road construction project and the area over which they are distributed, it is impractical to regularly check each light. In addition to these issues, non-rechargeable batteries must be disposed of properly. Failure to properly dispose of non-rechargeable batteries can lead to significant environmental problems due to leaching of the chemicals from the batteries.
Rechargeable batteries have many of the same problems as non-rechargeable batteries, including unpredictable lifespan and disposal. Rechargeable batteries are also generally more expensive than non-rechargeable batteries. Despite this, rechargeable batteries are preferred over non-rechargeable batteries by the fact that they are rechargeable, and therefore require fewer replacements, and in the long run are most cost effective. Since it is important to be able to recharge the rechargeable batteries in the field without having to actually remove them from the safety light, rechargeable batteries may be recharged by a solar cell array included with a safety light.
Despite this, there are still drawbacks. Rechargeable batteries may not fully charge during the sunlight hours, e.g., cloudy day. As such, the rechargeable batteries still face the very real possibility of running down during the night such that the safety light is not able to illuminate. In addition, some rechargeable batteries are known to suffer from battery memory. This refers to the situation in which certain types of batteries, such as Nickel Cadmium, batteries gradually lose their maximum energy capacity if they are repeatedly recharged after being only partially discharged.